thank you very much,
I think, you are right, But in an article I read that the
circumferential strain of cylinder when the cylinder is inner
pressurized is:
ec=P*(k2)^2*(2-v)/[(k2)^2-1]
the above expression is not equal to tangentional strain. I think these
are not equal.
Please let me know, if you would like to see the article.